[driver] make clear when the results dir becomes available

Summary:
The logic is not that simple and this will be needed in a later diff to create
the log file as early as possible.

Reviewed By: jberdine

Differential Revision: D5173128

fbshipit-source-id: 830f105

infer/src/backend/infer.ml

@@ -548,16 +548,28 @@ let differential_mode () =
   Unix.mkdir_p out_path;
   Differential.to_files diff out_path
 
+let assert_results_dir advice =
+  if Sys.file_exists Config.results_dir <> `Yes then (
+    L.stderr "ERROR: results directory %s does not exist@\nERROR: %s@." Config.results_dir advice;
+    exit 1
+  )
+
+let setup_results_dir () =
+  match Config.command with
+  | Analyze -> assert_results_dir "have you run capture before?"
+  | Clang | Report | ReportDiff -> create_results_dir ()
+  | Capture | Compile | Run  ->
+      (* These have their own logic depending on the rest of the command line. It particular they
+         might delete the previous results directory. Let them do their thing. *)
+      ()
+
 let () =
   if Config.print_builtins then Builtin.print_and_exit ();
+  setup_results_dir ();
   match Config.command with
   | Analyze ->
       Logging.set_log_file_identifier
         CommandLineOption.Analyze (Option.map ~f:Filename.basename Config.cluster_cmdline);
-      if Sys.file_exists Config.results_dir <> `Yes then (
-        L.stderr "ERROR: results directory %s does not exist@.@." Config.results_dir;
-        Config.print_usage_exit ()
-      );
       InferAnalyze.register_perf_stats_report ();
       analyze Analyze
   | Clang ->

infer/src/clang/Capture.re

@@ -42,8 +42,7 @@ let register_perf_stats_report source_file => {
   let stats_dir = Filename.concat Config.results_dir Config.frontend_stats_dir_name;
   let abbrev_source_file = DB.source_file_encoding source_file;
   let stats_file = Config.perf_stats_prefix ^ "_" ^ abbrev_source_file ^ ".json";
-  Utils.create_dir Config.results_dir;
-  Utils.create_dir stats_dir;
+  Unix.mkdir_p stats_dir;
   PerfStats.register_report_at_exit (Filename.concat stats_dir stats_file)
 };